"Follow the water." No Deep-Throated environmental informant actually whispers this advice to writer Jordan Fisher Smith late one night in a deserted campground, but the sentiment infuses "Nature Noir," his taut drama of life as a ranger in the Sierra.

Fisher Smith's book follows the tradition of nature writers such as Emerson, Thoreau, John Muir and Annie Dillard. But "Nature Noir" is no Emersonian ode to pastoral transcendentalism, nor is it a Muirian celebration of the sacred in the wilderness. The writer who most closely anticipates Fisher Smith's themes is Joan Didion, who wrote, in 1977, "some of us who live in arid parts of the world think about water with a reverence others might find excessive." Fisher Smith would probably find nothing unusual about this obsession. Because for the 14 years he worked the canyons of the American River, he lived under the daily specter of the ravine being flooded for a dam.

Fisher Smith does much to dispel the notion of park users as docile birdwatchers in hiking shorts or rangers as kindly wildflower guides in khaki hats. His job implies protecting the people from nature, but the reality is more often vice versa. The hunters, fishermen and miners he encounters are drawn to the recreation area not because of an inherent love of clean air and open sky, but because camping is a cheap way to live with little outside interference.

When he begins the job, another ranger explains he shouldn't try to collect campsite fees the first Thursday of the month, because it's "Cheese Day": the day the government doles out surplus food. Miners supplement these handouts with the flakes of gold they manage to dredge from the river bottom. Squatters manufacture illegal drugs in shacks hidden deep in the woods. Extreme recreators view the park as a giant obstacle course for their cars, off-road vehicles and parachutes.

One gets the sense in the first chapters that Fisher Smith's disinclination toward humans led him to become a ranger in the first place. Nearly every miscreant he tickets for an infraction is stringy-haired; every despoiler drives a beater car and drinks cheap beer. But slowly it becomes apparent that Fisher Smith has a larger agenda than complaining about disrespectful campers.

The sickness is not with the people who use the canyons, but within the river itself. Beginning with the Gold Rush, when farmers built diversion dams along the river to irrigate their fields, and the miners clear-cut forest and dug open-pit mines into the river bed, man tried to shape the river and surrounding canyons to his will, sometimes succeeding short term, but creating havoc for future generations, as the river resisted attempts to tame it. In the battle between man and the river, the river wins every time. But so far, man has not stopped fighting. The devastations of the Gold Rush led to floods and droughts during the industrialization of the early 20th century, prompting the creation of the Folsom Dam. Flooding of the Sacramento and American rivers in the 1950s and '60s threatened to burst the dam, and Congress responded by starting a new one.

By the time Fisher Smith arrives on the scene, the river itself is stressed, and the people enact the pressures. The human anecdotes he relates - - a rape, an unsolved murder, suicides -- and the "natural" disasters he recounts -- floods, droughts, mudslides, Lyme disease, cougar attacks -- more than suggest a cause and effect. It's not just the residents who feel the strain:

"For decades park professionals have worried that the sort of duties rangers grow used to in a recreation area -- controlling crowds, quelling drunken fights, and contending with an urban criminal element -- would change the fundamental nature of the ranger's role. What has been less widely- discussed are the effects of whole careers spent in manmade recreation area landscapes -- lifeguard towers, concrete-block restrooms, parking lots, snack bars, and the muddy bathtub rings from the changing water levels of reservoirs -- on the wilderness aesthetic of people in the ranger services."

Add to this the particular sense of futility that the rangers feel knowing the land they patrol may be flooded for the Auburn Dam (maps already show the area as one big lake), and Fisher Smith would be justified in having a fair amount of cynicism. But though he condemns the bureaucrats who hubristically dictate the fate of the American River and the lowlifes who despoil its canyons equally, his appreciation of the area itself remains unsullied. There are lovely, lyric passages in "Nature Noir" where Fisher Smith describes the scent of a late-afternoon summer breeze or the color of the leaves on an early spring dawn.

And the protracted limbo of his situation, working the "forty-eight miles of the American River lying beneath the waterline of the endlessly delayed Auburn Reservoir," give him a philosophic perspective well-suited to his thesis. As he writes, quoting Chinese prophet Lao-tzu, "Nothing in the world is as soft, as weak, as water; nothing else can wear away the hard, the strong, and remain unaltered."